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为了高效处理宽带非恒包络信号,利用宽带包络信号功率主要集中在低频部分的特性,结合线性放大器和开关类放大器的优势,设计了一个宽带包络跟踪放大器。该放大器由一个宽带线性级和一个受线性级控制的高效开关级组成。线性级采用折叠式共源共栅放大器结构,具有AB类输出级及输出级缓冲;开关级采用同步降压型DC-DC变换器结构,包含驱动电路及“防直通”模块。整个电路采用Jazz 0.18μm BiCMOS工艺进行设计仿真,结果表明,在3.3V电源电压下,线性级单位增益带宽约为50MHz,可驱动300mA电流,具有188V/μs的摆率,包络跟踪放大器可跟踪包络信号幅度和带宽的瞬时变化,改变开关导通比以及开关频率。
In order to deal with the broadband non-constant envelope signal efficiently, a broadband envelope tracking amplifier is designed based on the advantage that the broadband envelope signal power is mainly concentrated in the low-frequency part. Combining the advantages of the linear amplifier and the switching amplifier, a broadband envelope tracking amplifier is designed. The amplifier consists of a wideband linear stage and a linear stage-controlled high-efficiency switching stage. The linear stage adopts a folded cascode amplifier structure with a class AB output stage and an output stage buffer. The switching stage adopts a synchronous step-down DC-DC converter structure, including a driving circuit and an anti-thru-through module. The whole circuit is designed and simulated by Jazz 0.18μm BiCMOS process. The results show that the linearity unit gain bandwidth is about 50MHz at 3.3V supply voltage, which can drive 300mA current with a slew rate of 188V / μs. The envelope tracking amplifier can track The instantaneous change in envelope amplitude and bandwidth changes the switch turn-on ratio and the switching frequency.